Heretofore, a learning method, in which a comparison between an engine speed and a clutch input speed, when gradually engaging a start-up clutch, is made, and then the hydraulic pressure supplied to the clutch at the time when the clutch input speed has dropped by a predetermined revolution speed with respect to the engine speed is learned as a torque transmission point, is generally known (for instance, see Patent document 1).
Recently, in a lock-up clutch incorporated in a torque converter, both of a rapid engagement for improved fuel economy and a reduction of unnatural feeling that the driver experiences uncomfortable fluctuations of vehicle behavior when engaging the lock-up clutch are required. For this reason, learning of a torque transmission point has been studied even in a lock-up clutch. For instance, application of learning control for a start-up clutch, as disclosed in the Patent document 1, would be considered.
However, assuming that torque-transmission-point learning control for a lock-up clutch is performed during traveling for the purpose of ensuring a learning frequency, there is a case where the engine speed fluctuates irrespective of an engaged state of the lock-up clutch. That is, there is a possibility of erroneous learning.
It is, therefore, in view of the previously-described drawbacks of the prior art, an object of the invention to provide a vehicle lock-up clutch control device and lock-up clutch control method in which erroneous learning is prevented while ensuring a learning frequency, when performing learning control based on information on a meet point at which a lock-up clutch starts torque transmission.